This application is based upon and claims priority of Japanese Patent Applications Nos. 2000-277100, 2000-177368,2000-114024,2000-22217, and 2001-18340, all the contents being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a sheet-like display, a sphere-like resin body, and a microcapsule, and more particularly to a flexible sheet-like display, a sphere-like resin body constituted of two parts, and a microcapsule containing a sphere-like body.
In this specification, the sphere-like body has a shape like a sphere and is a small object capable of rotating in a limited space, this small object including a small object made of two small sphere-like objects coupled together.
2. Description of the Related Art
With recent developments of information societies, so-called multimedia information such as characters, images and sounds is frequently used in various information processing apparatus. Technical advancement of printers for outputting print information to a paper sheet is remarkable. A large quantity of paper used for drafts for manuscripts, conference materials, memorandums for messages and circulares, or the like is dumped after it is used during a temporary short time. Paper used for tickets for vehicles, price tags attached to goods in shops, or the like is also dumped after it is used temporarily and this quantity is not negligible.
Environmental questions resulting from mass consumption of paper are ventilated in public, such as disruption of natural environments typically exhausted forest resources and poison containing chroline compounds formed at garbage furnaces. Under such social environments, reducing the consumption of paper resources is a matter requiring immediate attention. One method of reducing the consumption of paper resources is a reuse of them. The current reuse of paper resources is mainly to utilize used paper as a material of new paper. Another method of reducing the consumption of paper is to supply new reusable resources which can be substituted for paper.
Many display element sheets called electronic sheets, sheet-like displays or the like have been proposed. Such a display element sheet displays a desired image by disposing sheet-like display elements between electrodes and applying an electric field or magnetic field. Following display sheets are mainly known.
(1) A turn-round spherical body distribution type display element sheet in which small sphere-like bodies are distributed in elastomer and an electric field is applied to display a desired image, the sphere-like body having two color portions and being capable of turning round in accordance with the direction of an electric field.
(2) An electrophoretic particle dispersion type display element sheet in which a display layer is formed by dispersing electrophoretic particles in dielectric (electrically insulating) liquid, and the optical characteristics of the display layer are changed by changing the dispersion state of electrophoretic particles by an electric field to display a desired image.
(3) An intra-microcapsule rotor type display element sheet (JP-A-7-343133) in which microcapsules are used each containing a rotator formed by coupling semispheres having different colors and electric characteristics, and an electric field is applied through the microcapsule to rotate the rotor and display a desired image.
(4) An intra-microcapsule electrophoretic particles type display element sheet (JP-A-1-86116, U.S. Pat. No. 2,551,783) in which a microcapsule filled with electrophoretic particles and coloring solvent, and an electric field is applied to the electrophoretic particles via the microcapsule to change the distribution of electrophoretic particles and the optical characteristics of the microcapsule to display a desired image.
(5) A film liquid crystal type display element sheet in which liquid crystal is sandwiched between films.
(6) A display element sheet using a composite film of liquid and polymer, the liquid is smetic liquid with dichronic dyes.
These display element sheets have a memory performance, can store image information at least some period without any power source, and are of a reflection type. These display elements are therefore expected as a substitute for paper. The display element sheet can be formed by coating material on a film with electrodes such as polyethylene terephthalate PET. It is therefore suitable for a sheet-like display which is thin, light and portable.
A sphere-like body rotating type display element is disclosed in the specifications of U.S. Pat. Nos. 4,126,854 and 4,143,103. A sphere-like body made of semispheres having different colors can be formed by coloring half areas of a sphere-like body made of wax with pigment. This manufacture method is described in JP-A-6-226875. With this method, a sphere-like body is manufactured in the following processes. Two types of melted wax are prepared, one type being colored in black with inorganic black pigment and the other type being colored in white with inorganic white pigment. The same amount of white and black wax is supplied to nozzles disposed under and over a rotating disk. Wax on the rotating disk flies away from the rotating disk in the form of wax droplet by a centrifugal force. Wax droplet is cooled through contact with air and solidified. By using a microcapsule containing this sphere-like body and oil, a display element is formed. By holding the display element by a support, an external voltage is applied to display an image.
The sphere-like body manufacture method is complicated because it has many control parameters such as a disc rotation speed, a melted wax temperature and a cooling air temperature. With this manufacture method, it is not necessarily possible to form a spherical body made of perfect semispheres of two colors, and the shape of the sphere-like body is not ideal.
JP-B-50-15115 discloses an electrophoretic particle sealed type display element. This element is formed by sealing dye, dielectric liquid, electrophoretic titanium dioxide particles in a cell. This method is, however, associated with some problems that dye is faded on an electrode and titanium dioxide particles are coagulated. These problems have been solved by JP-A-64-86116 which proposes to seal dye, dielectric liquid and titanium dioxide in a microcapsule.
As a microcapsule preparation method, there are a phase separation method, an interfacial polymerization method, an insolubilization method and the like. For example, JP-A-5-317805 teaches a phase separation method, more particularly a complex coacervation method for gum arabicxe2x80x94gelatin series.
It is desired to prevent leakage of dielectric solution in order to use a sphere-like body which is rotated by electrophoretic particles sealed in a microcapsule-or an electric field. To this end, it is preferable to make the film of a microcapsule thick to increase a rupture strength. However, for example, with the interfacial polymerization method, polymerization occurs only at the interface between an oil phase and a liquid phase so that only a very thin film (near a monomolecular layer) is formed.
If the coacervation method of the phase separation method is adopted, the film of a microcapsule can be made thick. However, in order to harden a film, a temperature is required to be controlled in a minute unit, pH is required to be controlled by dispensing droplets of alkaline solution, and hormaldehyde which is acute toxic substance is required to be added. Further, polymerization reaction by this method is unstable so that there is a possibility that the formed film extinguishes unless pH adjustment and density adjustment are performed continuously.
If a film liquid crystal type display element is used, a thin display device can be obtained. However, as compared to other sheet-like display elements such as an electrophoretic particle dispersion type display element and a microcapsule type display element, a retention performance of displayed information is inferior, a flexibility is small, and folding is difficult.
A conventional display element sheet and a peripheral circuit are discrete components. The peripheral circuit includes a power source, a driver and a controller. The display sheet and peripheral circuits are connected by using cables or a flexible circuit board. This hinders compactness, light weight and low cost. A method of forming a driver (circuit) by flexible plastic transistors made of coated organic material by screen printing or the like, has been proposed and studied. This proposal aims to replace printed paper sheets and conventional displays.
If a combination of discrete display elements and peripheral circuits is used in manufacture lines, there is essentially a limit of size and shape, particularly a limit of broadening a display area and thinning the display device. Therefore, conventional display element sheets cannot realize the use state just like paper sheets.
A display element of a sheet-like display device is generally made of an image display layer sandwiched between two laminated layers each having a base film of plastic such as PET on which conductive material such as indium tin oxide (ITO) or resin is coated. Displayed image is viewed through one laminated layer. Since the plastic film on the surface (display surface) of the display element has high luster, a visual texture like paper and a proper contrast are difficult to be obtained. Further, since two laminated films are used, the display device becomes thick.
A display device without electrodes on the display surface side is known. Such display devices using rotating bodies are under developments as described in M. E. Howard et al., xe2x80x9cGyricon Electric Paperxe2x80x9d, in Digest of Technical Papers of SID Int. Symposium (1998). Display devices of an electrophoresis type are under developments as described in H. Kawai et al., xe2x80x9cMicrocapsule-type Electrophoretic Displayxe2x80x9d, Japan Hardcopy ""99. Display devices of a liquid crystal-polymer composite film type are under developments as described in K. Sekine et al., xe2x80x9cRewritable Medium Using Polymer Dispersed Liquid Crystal Filmsxe2x80x9d, Japan Hardcopy ""99.
Such display devices have data write external electrodes which are formed on the display surface. It is therefore desired to planarize the display surface in order to increase tight adhesion to the external electrodes. Therefore, luster of the display surface becomes high so that a texture like paper and a sufficient contrast are difficult to be obtained.
A method of writing data by blowing ions without forming electrodes on the display surface side and without using external electrodes, has been proposed as disclosed in K. Ogawa et al., xe2x80x9cMicrocapsule Electrophoretic Display Method Using Ion Projection Headxe2x80x9d, in Digest of Technical Papers of SID Int. Symposium (1999). In this case, an apparatus for generating an ion flow is required. As compared to a method of writing data by using external electrodes connected to only a power source, simplicity and cost are inferior.
Conventional sheet-like display devices are not still sufficiently convenient to use. New technology has long been waited in order to realize a sheet-like display device convenient to use.
It is a first object of the invention to provide a large screen and thin type sheet-like display device capable or realizing a use state like paper.
It is a second object of the present invention to provide a sphere-like resin body which is easy to manufacture, constituted of two semisphere-like small bodies capable of being colored differently, and has a substantially sphere shape.
It is a third object of the present invention to provide a microcapsule which contains electrophoretic particles or a sphere-like body in a shell having a high breaking strength, is easy and safe to manufacture, and suitable for application to a sheet-like display device.
It is a fourth object of the present invention to provide a sheet-like display device capable of realizing a texture like paper and a sufficient contrast and having a thickness reduced to a practically usable level.
According to a first aspect of the present invention, there is provided a sheet-like display device comprising: a flexible sheet-like display layer; and at least one flexible electric layer formed integrally with the sheet-like display layer, the electric layer including electric function components for functioning the display layer.
According to a second aspect of the present invention, there is provided a sphere-like resin body comprising first and second portions, the first portion being made of first resin having a solubility parameter xcex41, the second portion being made of second resin having a solubility parameter xcex42, and an absolute value of a difference between both the solubility parameters being |xcex41xe2x88x92xcex42|xe2x89xa70.2.
According to a third aspect of the present invention, there is provided a microcapsule having a shell made of resin in which together with dielectric liquid, particles capable of moving under an electric field or a magnetic field, or a core including a sphere-like body capable of rotating under an electric field or a magnetic field, whose semispheres have different colors and different electromagnetic characteristics, wherein a diameter of the core is in a range from 10 xcexcm to 200 xcexcm and a circumferential length L of the microcapsule is in a range of (4.1xc3x97T)xe2x89xa6Lxe2x89xa6(20.1xc3x97T) where T is a Martin diameter of the microcapsule.
According to a fourth aspect of the present invention, there is provided a sheet-like display device comprising: a base; a pair of opposing electrodes formed on the base; and a display layer disposed between the opposing electrodes, the display layer being capable of changing optical characteristics under a potential difference between the opposing electrodes and having surface roughness, wherein of the opposing electrodes, the electrode on a display surface side is made of a conductive resin layer adjacent to the display layer and a surface shape is conformal to the surface roughness of the display layer.
Various electric function elements and circuits such as a display function element, a power source element, a driver circuit, a control circuit, a communication circuit and an acoustic signal conversion are formed in the same sheet. A sheet-like display device can therefore be provided which can provide the use states just like paper and has a large display area.
Such a sheet-like display device can be manufactured at a low cost by omitting wiring members necessary for connection of elements and circuits and molding or packaging members necessary for elements and circuits, and by standardizing and simplifying manufacture processes.
By using sheet-like display devices, a consumption amount of paper sheets can be reduced easily, and various merits such as the protection of environment of the Earth with less consumption of resources and cost reduction can be expected.
A sheet-like display device having the integrated structure of a display layer and electrodes can have the texture more like paper. If solvent soluble conductive resin material is used for this display device, the electrodes can be formed by coating resin solution and the manufacture efficiency can be improved.
The invention provides a sphere-like resin body substantially having a sphere shape and constituted of two semispheres having different colors, and a microcapsule containing the sphere-like resin body and being usable as a display element of a sheet-like display device. The sphere-like resin body and microcapsule can be manufactured by a simple manufacture method.
The invention also provides a microcapsule which contains electrophoretic particles, can be manufactured by simple processes without using toxic materials, has a thick shell and a high rupture strength, and is suitable particularly for use with a sheet-like display device.